As a result, modern science is prevented from conceiving any valid idea of 'force'. In so far as the concept 'force' appears in scientific considerations, it plays the part of an 'auxiliary concept', and what man naively conceives as force has come to be defined as merely a 'descriptive law of behaviour'. We must leave it for later considerations to show how the scientific mind of man has created for itself the conviction that the part of science occupied with the actions of force in nature can properly be treated with purely kinematic concepts. It is the fact itself which concerns us here. In respect of it, note as a characteristic of modern text-books that they often simply use the term 'kinetics' (a shortening of kinematics) to designate the science of 'dynamics'.⁴